Power and pressure effects upon magnetron sputtered aluminum doped ZnO films properties

Abstract

In this work, polycrystalline aluminum doped zinc oxide (ZnO:Al) films with c-axis (002) orientation have been grown on glass and silicon substrates by RF (radio frequency) magnetron sputtering technique, at room temperature. A systematic study of the effect of sputtering deposition parameters (i.e. RF power and argon gas pressure) on the structural, optical and electrical properties of the films was carried out. We observed that, with increasing RF power the growth rate increased, while it decreased with increasing gas pressure. As mentioned above, the films were polycrystalline in nature with a strong preferred (002) orientation. The intrinsic compressive stress was found to decrease with both increasing RF power and gas pressure, and near stress-free film was obtained at 200 W RF power and 2 × 10 − 1 Pa gas pressure. The obtained ZnO:Al films, not only have an average transmittance greater than 90% in the visible region, but also have an optical band gap between 3.33 and 3.47 eV depending on the sputtering parameters. Moreover, a low value of the electrical resistivity (~ 1.25 × 10 − 3 Ω cm) was obtained for the film deposited at 200 W and 2 × 10 − 3 mbar.